Personally I use a Fluke DVM and I load it like KW Counter does. It is more accurate than the Expanded scale Hobbico meter.

The reason manfactures put in a blocking diode is for protection from reverse charging your transmitter. I.E. trying to charge the battery with the charger negative lead to the positive lead of the charger. With the blocking diode nothing happens, without it the smoke comes out. Another method is to fuse the positive jack and then put a diode wired as a shunt to ground. In case of reverse polarity the fuse blows. The newer radios use a resettable solid state fuse.

Bypassing the diode has no ill effects other than cancelling the protection it afforded in the first place.

John